This invention relates to lock mechanisms of the kind used with deadbolt assemblies intended to secure a movable member, such as a door, in a closed position at which it prevents access to a space at one side (usually the inside) of the door or other member. It will be convenient to hereinafter describe the invention with particular reference to doors, but it is to be understood that the invention has wider application.
Deadbolt assemblies of the foregoing kind generally have two rotatable actuators which are operable at the inside and the outside of the door respectively. The outside actuator is usually in the form of a key operated lock, whereas the inside actuator usually includes a manually operable turn knob. It is desirable that the key operated lock at the outside of the assembly be arranged to turn through 360xc2x0 in moving the deadbolt between operative and inoperative positions. The inside actuator however, may require less movement (e.g., 180xc2x0 rotation) to achieve the same result, and the lock mechanism needs to permit the different movement requirements of the two actuators.
Various means have been adopted to address the foregoing problem. One lock mechanism which has proven to be particularly satisfactory is that disclosed by Australian Patent 601098, but that mechanism is relatively complicated. The prior mechanism is expensive to manufacture because it requires a large number of parts and is difficult to assemble by automatic means.
It is an object of the present invention to provide a deadbolt lock mechanism of relatively simple form which requires a minimum number of parts and which is relatively easy to assemble.
A lock mechanism in accordance with the present invention is characterised in that it includes a gear train through which each of the two actuators is drivably connected to the deadbolt. The gear train includes two drive gears which are rotatable independent of one another, at least to some extent, and each of which is adapted to be caused to rotate by a respective one of each of the two actuators. Each of the two drive gears is cooperable with a composite gear which also forms part of the gear train and which is drivably connected to the deadbolt so as to move the deadbolt between its operative and inoperative positions.
The arrangement is preferably such that the composite gear rotates through 180xc2x0 in moving the deadbolt between its operative and inoperative conditions, and such 180xc2x0 movement occurs regardless of which of the two actuators is operated. In particular, the 180xc2x0 composite gear movement occurs when driven by the drive gear connected to the outside actuator even though that drive gear may rotate through 360xc2x0.
In a preferred arrangement, the composite gear includes two gears interconnected for simultaneous rotation about a common axis. The two gears may be formed integral or otherwise secured together for that purpose. It is further preferred that a drive member, such as a pin, is connected to the composite gear and cooperates with the deadbolt in a manner such that the deadbolt moves linearly in response to rotation of the composite gear.
The gear train and the deadbolt may be housed within a hollow casing, and in one arrangement it is preferred that the deadbolt cooperates with the casing so as to be guided along a straight path when moving between the operative and inoperative positions. The gear train is preferably arranged to be loaded, in sub-assembly form, into the casing through an open side of the casing. The loading operation can be performed automatically and has the effect of placing the composite gear in drivable engagement with the deadbolt. A removable cover plate may be attached to the casing to extend over the aforementioned open side and thereby retain the gear train in place.
Reference to xe2x80x9cgearxe2x80x9d throughout this specification is to be understood as embracing a rotatable member having teeth extending around part only of its periphery. That is, the word xe2x80x9cgearxe2x80x9d embraces any rotatable member having a gear-like function during at least part of a complete revolution of movement of that member about its axis of rotation.